Fingerprint imaging recognition technology is used to realize identification by capturing fingerprint images of a person using optical fingerprint sensors and then determining whether the fingerprint images match those stored in a system before. Due to its convenience in use and uniqueness of human fingerprints, the fingerprint recognition technology has been widely applied to various fields, such as safety inspection field (for example, public security bureau or customs), entrance guard systems in buildings, consumption goods field (for example, personal computers or mobile phones), and the like. The fingerprint recognition technology includes optical imaging, capacitive imaging, ultrasonic imaging and the like, among which, the optical fingerprint recognition technology is advantageous in imaging quality and device cost.
As shown in FIG. 1, an existing optical fingerprint module includes a backlight source 110, an optical fingerprint sensor 120, a protective layer 130 and a shell (not shown is FIG. 1). To acquire a fingerprint image, a finger 140 of a person is placed on the protective layer 130. Output light 111 of the backlight source 110 (upward arrows in FIG. 1 represent the output light 111, and the upward arrows are surrounded by dotted lines to be marked in a unified manner) penetrates through the optical fingerprint sensor 120 and the protective layer 130, and is reflected and transmitted at a contact interface between the finger 140 and the protective layer 130. Reflected light 112 (downward arrows in FIG. 1 represent the reflected light 112, and the downward arrows are surrounded by dotted lines to be marked in a unified manner) penetrates through the protective layer 130 and irradiates onto the optical fingerprint sensor 120. Circuits (not shown in FIG. 1) inside the optical fingerprint sensor 120 perform photoelectric conversion and signal processing to realize acquisition of the fingerprint image. As a contact part between the finger 140 and the protective layer 130 reflects fingerprint characteristics of the person, and characteristic of the contact part can directly indicate characteristic of the reflected light 112, the image acquired by the optical fingerprint sensor 120 directly reflects the fingerprint characteristics of the person.
More content related to optical fingerprint sensors can be found in Chinese Utility Model Patent with a publication No. CN203405831U.
Structures and performance of existing optical fingerprint modules need to be improved.